Billionaire investor George Soros' hedge fund reported on Friday holdings valued at $4.2 billion as of June 30 as it reduced its presence in the energy sector.

Soros Fund Management LLC, whose holdings were worth $4.51 billion at the end of March 31, significantly reduced its stake in its top holding, the Brazilian state-run energy company Petrobras (PBR), according to the fund's disclosure with the Securities and Exchange Commission.

The fund reduced its stake in Petrobras to 9.8 million American depository receipts, valued at $402.4 million. It also reported 5.9 million non-voting ADRs in Petrobras valued at $196.3 million. As of the end of the first quarter, the fund owned 31.6 million ADRs of the company valued at $962.9 million.

Soros further cut its exposure to energy by dropping oil company ConocoPhillips (COP). The fund owned 4.1 million shares as of the end of the first quarter.

Among its other large holdings, Soros cut its stake in fertilizer-maker Potash Corp. of Saskatchewan Inc. (POT) to 2 million shares from 5.7 million in the first quarter. The stake is valued at $184 million as of June 30.

The fund also cut its stake in Wal-Mart Stores Inc. (WMT) to 89,710 shares, valued at $4.3 million, from 1.8 million shares.

Soros did buy auto-parts retailer Autozone Inc. (AZ), adding 523,000 shares, as well as 202,000 shares of Burger King Holdings Inc. (BKC).

-By Roger Cheng, Dow Jones Newswires; 212-416-2153; roger.cheng@dowjones.com